As users have rapidly increasing requirements for network traffic and bandwidths, operators are also increasingly urgent to implement an intelligent scheduling function of a bottom-layer wavelength division multiplexing (WDM) network in an optical communication network.
In a transmission process of an optical signal, a power of the optical signal may have a nonlinear gain or attenuation, resulting in various problems in network management. For example, an excessively high power of the optical signal may result in greater nonlinear transmission costs, and an excessively low power of the optical signal results in an excessively small signal-to-noise ratio of signal light of a receive end. Therefore, in the transmission process of the optical signal, the power of the optical signal needs to be adjusted to fall within a specified power range. For example, for an 80-channel system having 80 communication bands, in a system specification, for each transmission span, a power value of an optical signal in a channel corresponding to each band is required to be +1 decibel milliwatt dBm.
A power of a to-be-adjusted optical signal may be adjusted by adding an insertion loss to the optical signal. In a specific method, when the optical signal passes through a reconfigurable optical add-drop multiplexer (ROADM) node constructed by a wavelength selective switch (WSS) device, a diffraction direction of an input optical signal whose power needs to be adjusted is controlled by using liquid crystal on silicon (LCOS) in the WSS device, so that only a part of the optical signal is output from a target output port, and the optical signal is attenuated.
FIG. 1 is a schematic diagram of an optical path of a power adjusting method. When the signal light is deflected toward an outer edge of the target output port by an angle, crosstalk light is also deflected. In such a method, although a power of an optical signal can be attenuated, high-order diffractive light, generated after deflection processing, that is the crosstalk light, is also deflected. When the crosstalk light approaches to another output port, crosstalk energy coupled to the other output port increases. Consequently, isolation between ports decreases.